Area below Whisker menu is shifted left

When i click the whisker icon on the Xfce panel to show the Whisker menu whatever is in the square area where the menu will appear is shiftet some pixels to the left for what seems to be about 200 ms each time just before the menu appears.

If i drag the whisker menu wider to fill the width of the screen the shift is greater.

xfce4-whiskermenu-plugin 2.4.6 Xfce 4.14 Linux Mint 20.1